The present invention relates to a technique for measuring an elasticity index of a blood vessel using an ultrasonic wave, and evaluating and determining the reliability of the elasticity index. In particular, the present invention relates to an ultrasound diagnostic apparatus, a method of determining elasticity index reliability, and a program for determining elasticity index reliability which determine the reliability of an elasticity index of a blood vessel obtained by measurement using an ultrasonic wave.
In order to perform non-invasive cardiac diagnosis on the basis of acoustic and elastic characteristics of the heart muscle, it is necessary to percutaneously measure microvibrations having an amplitude equal to several tens of μm or less in each site of a heart wall over a frequency band up to hundreds of Hz consecutively over several beats. Accordingly, a technique is known in which the instantaneous position of a vascular wall is determined using the amplitude and phase of a detected signal, and the large amplitude displacement motion of the vascular wall based on a heart stroke is tracked, thereby obtaining the elastic modulus of a blood vessel (see JP 10-5226 A). Specifically, the motion rate waveform of microvibrations of a vascular wall is obtained on the basis of the sequential position of the vascular wall, tracking loci of parts taken at predetermined intervals in the depth direction of the vascular wall are obtained, and temporal changes in thickness of the parts are calculated, thereby obtaining the elastic modulus of a blood vessel.